Electromagnetic pump

ABSTRACT

An electromagnetic pump including a piston that reciprocates inside a cylinder; an electromagnetic portion and a biasing member that respectively forwardly and backwardly move the piston; a support for the biasing member that defines a chamber with the cylinder and the piston; a valve incorporated into the support member that allows fluid to move from an intake port to the chamber and prohibits reverse flow; and a valve that allows the fluid to move from the chamber to a discharge port and prohibits reverse flow. The support member includes a bottomed hollow portion accommodating at least a portion of the intake on-off valve, and a hole providing communication between a bottom portion of the hollow portion on the chamber side and the chamber. The support member includes a portion that supports the biasing member, and a portion that communicates with the hole and projects from the support toward the piston.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-068808 filed onMar. 25, 2011 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an electromagnetic pump including: acylinder; a piston that can reciprocate inside the cylinder; anelectromagnetic portion that forwardly moves the piston; a biasingmember that backwardly moves the piston; a support member that supportsthe biasing member and, with the cylinder and the piston, defines a pumpchamber; an intake on-off valve that is incorporated into the supportmember, and allows a hydraulic fluid to move from an intake port to thepump chamber and prohibits reverse movement of the hydraulic fluid; anda discharge on-off valve that allows the hydraulic fluid to move fromthe pump chamber to a discharge port and prohibits reverse movement ofthe hydraulic fluid.

DESCRIPTION OF THE RELATED ART

A past example of this type of electromagnetic pump (e.g., see JapanesePatent Application Publication No, JP-A-2011-21593) includes: acylinder; a piston that reciprocates inside the cylinder to change thevolume inside a pump chamber; a solenoid portion that forwardly movesthe piston; a spring that backwardly moves the piston; an intake checkvalve that allows a hydraulic fluid to move from an intake port to thepump chamber and prohibits reverse movement of the hydraulic fluid; anda discharge check valve that allows the hydraulic fluid to move from thepump chamber to a discharge port and prohibits reverse movement of thehydraulic fluid. According to this electromagnetic pump, the intakecheck valve and the discharge check valve are accommodated inside thecylinder. The intake check valve is configured from a ball; a hollowcylindrical body that accommodates the ball therein, and is formed withan axially center hole that provides communication between the intakeport and the pump chamber and forms an opening portion of the intakeport with an inner diameter smaller than the outer diameter of the ball;a spring that biases the ball with respect to the opening portion of theintake port in a direction opposite from the direction in which thehydraulic oil flows from the intake port; and a spring seat thatreceives the spring. In the intake check valve, the spring seat facesthe pump chamber, and a surface of the spring seat on the pump chamberside also supports the spring that backwardly moves the piston.

SUMMARY OF THE INVENTION

In the type of electromagnetic pump described above, the piston and theintake check valve are accommodated facing one another inside thecylinder, and the pump chamber is defined by the cylinder, the piston,and the intake check valve. Therefore, how the intake check valve isconfigured is an extremely critical factor for determining the volume ofthe pump chamber and also determining the biasing force of the springaccommodated inside the pump chamber.

An electromagnetic pump of the present invention further improvesdischarge performance.

The electromagnetic pump of the present invention employs the followingto achieve the above.

An electromagnetic pump according to the present invention includes: acylinder; a piston that can reciprocate inside the cylinder; anelectromagnetic portion that forwardly moves the piston; a biasingmember that backwardly moves the piston; a support member that supportsthe biasing member and, with the cylinder and the piston, defines a pumpchamber; an intake on-off valve that is incorporated into the supportmember, and allows a hydraulic fluid to move from an intake port to thepump chamber and prohibits reverse movement of the hydraulic fluid; anda discharge on-off valve that allows the hydraulic fluid to move fromthe pump chamber to a discharge port and prohibits reverse movement ofthe hydraulic fluid. In the electromagnetic pump, the support memberincludes therein a bottomed hollow portion accommodating from the intakeport side at least a portion of the intake on-off valve, and acommunication hole providing communication between a bottom portion ofthe hollow portion on the pump chamber side and the pump chamber. Inaddition, the support member is formed with a support portion thatsupports the biasing member, and a projection portion that is incommunication with the communication hole and projects from the supportportion toward the piston side.

According to the present invention, the electromagnetic pump includes: acylinder; a piston that can reciprocate inside the cylinder; anelectromagnetic portion that forwardly moves the piston; a biasingmember that backwardly moves the piston; a support member that supportsthe biasing member and, with the cylinder and the piston, defines a pumpchamber; an intake on-off valve that is incorporated into the supportmember, and allows a hydraulic fluid to move from an intake port to thepump chamber and prohibits reverse movement of the hydraulic fluid; anda discharge on-off valve that allows the hydraulic fluid to move fromthe pump chamber to a discharge port and prohibits reverse movement ofthe hydraulic fluid. In the electromagnetic pump, the support memberincludes therein a bottomed hollow portion accommodating from the intakeport side at least a portion of the intake on-off valve, and acommunication hole providing communication between a bottom portion ofthe hollow portion on the pump chamber side and the pump chamber. Inaddition, the support member is formed with a support portion thatsupports the biasing member, and a projection portion that is incommunication with the communication hole and projects from the supportportion toward the piston side. Thus, the spacing for supporting thebiasing member can be set by the support portion, and the volume insidethe pump chamber can be controlled by the projection portion, therebyfurther improving discharge performance.

In the electromagnetic pump of the present invention described above, adiameter of the projection portion on the piston side may be formedsmaller than a diameter of the projection portion on the support portionside. In the electromagnetic pump according to this aspect of thepresent invention, the projection portion may be formed into a truncatedconical shape. Thus, processing of the support member can be madeeasier.

In the electromagnetic pump of the present invention, the hydraulicfluid may be discharged by the biasing member backwardly moving thepiston. Since the biasing force of the biasing member exhibits lessvariation due to temperature compared to the electromagnetic force, theaxial length of the electromagnetic pump can be shortened by using thebiasing force to discharge the hydraulic fluid, and application of thepresent invention enables further shortening of the axial length.

In the electromagnetic pump of the present invention, the hollow portionof the support member may be formed such that the bottom portion is moretoward the piston side than a support surface of the support portion.Thus, the length of the support member in the axial direction can beshortened and the overall pump can be downsized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram that shows the overall configuration ofan electromagnetic pump 20 as an embodiment of the present invention;

FIG. 2 is a perspective view of a piston 50 and an intake check valve 60inserted inside a cylinder 42; and

FIG. 3 is an exterior view that shows the exterior of a valve body 62.

DETAILED DESCRIPTION OF THE EMBODIMENT

Next, an embodiment of the present invention will be described.

FIG. 1 is a structural diagram that shows the overall configuration ofan electromagnetic pump 20 as an embodiment of the present invention. Asshown in the figure, the electromagnetic pump 20 of the embodiment isconfigured as a piston pump that reciprocates a piston 50 topressure-feed a hydraulic oil. The electromagnetic pump 20 also includesa solenoid portion 30 that generates an electromagnetic force, and apump portion 40 that operates by the electromagnetic force of thesolenoid portion 30. The electromagnetic pump 20 is incorporated into avalve body as a portion of a hydraulic circuit for turning on and off aclutch or a brake provided in an automatic transmission mounted in anautomobile, for example.

The solenoid portion 30 has a case 31 as a bottomed cylinder member onwhich an electromagnetic coil 32, a plunger 34 as a movable element, anda core 36 as a fixed element are disposed. Applying a current to theelectromagnetic coil 32 forms a magnetic circuit in which magnetic fluxcircles the case 31, the plunger 34, and the core 36, whereby theplunger 34 is suctioned and presses out a shaft 38 that is in contactwith a proximal end of the plunger 34.

The pump portion 40 includes: a hollow cylindrical cylinder 42 that isjoined to the solenoid portion 30; the piston 50 that is slidablydisposed inside the cylinder 42, and has a base end surface that iscoaxial with and contacts a proximal end of the shaft 38 of the solenoidportion 30; a spring 46 that contacts a proximal end of the piston 50,and applies a biasing force in a direction opposite from the directionin which the solenoid portion 30 applies an electromagnetic force; anintake check valve 60 that supports the spring 46 from a side oppositefrom the proximal end surface of the piston 50, and allows the hydraulicoil to flow in the suctioning direction toward a pump chamber 41 andprohibits the hydraulic oil from flowing in the reverse direction; adischarge check valve 70 that is embedded in the piston 50, and allowsthe hydraulic oil to flow in the discharging direction from the pumpchamber 41 and prohibits the hydraulic oil from flowing in the reversedirection; a strainer 47 that is disposed upstream of the intake checkvalve 60, and catches foreign matter included in the hydraulic oil thatis suctioned toward the pump chamber 41; and a cylinder cover 48 thatcovers an opening portion 42 a on a side of the cylinder 42 oppositefrom the solenoid portion 30 with the piston 50, the discharge checkvalve 70, the spring 46, the intake check valve 60, and the strainer 47incorporated in that order from the opening portion 42 a. Spiral groovesare formed in the circumferential direction on an inner circumferentialsurface of the cylinder cover 48 and an outer circumferential surface ofthe opening portion 42 a of the cylinder 42. Threadedly fastening thecylinder cover 48 with the opening portion 42 a of the cylinder 42attaches the cylinder cover 48 to the opening portion 42 a of thecylinder 42. Note that, in the pump portion 40, an intake port 49 forsuctioning the hydraulic oil is formed at an axial center of thecylinder cover 48, and a discharge port 43 for discharging the suctionedhydraulic oil is formed in a side surface of the cylinder 42.

The piston 50 is formed from a cylindrical piston body 52, and acylindrical shaft portion 54 b that has an outer diameter smaller thanthe piston body 52 and an end surface that contacts the proximal end ofthe shaft 38 of the solenoid portion 30. The piston 50 moves inassociation with the shaft 38 of the solenoid portion 30 andreciprocates inside the cylinder 42. A cylindrical, bottomed hollowportion 52 a that can accommodate the discharge check valve 70 is formedat an axial center of the piston 50. The hollow portion 52 a of thepiston 50 runs from a proximal end surface of the piston 50 to insidethe piston body 52, and extends to partway inside the shaft portion 54.In addition, two through holes 54 a, 54 b that intersect at a 90-degreeangle in the radial direction are formed in the shaft portion 54. Thedischarge port 43 is formed around the shaft portion 54, and the hollowportion 52 a of the piston 50 is provided in communication with thedischarge port 43 through the two through holes 54 a, 54 b.

The intake check valve 60 includes: a valve body 62 that is fitted byinsertion to an inner circumferential surface of the opening portion 42a of the cylinder 42, formed therein with a bottomed hollow portion 62a, and formed with a center hole 62 b that provides communicationbetween the hollow portion 62 a and the pump chamber 41 at an axialcenter of the bottom of the hollow portion 62 a; a ball 64; a spring 66that applies a biasing force to the ball 64; and a plug 68 that isfitted by insertion to an inner circumferential surface of the hollowportion 62 a with the ball 64 and the spring 66 incorporated into thehollow portion 62 a of the valve body 62.

FIG. 2 is a perspective view of the piston 50 and the intake check valve60 inserted inside the cylinder 42, and FIG. 3 is an exterior view thatshows the exterior of the valve body 62. As shown in the figures, thevalve body 62 is formed from a stepped structure that includes acylindrical base portion 63 a and a truncated conical projection portion63 b that projects from a seat surface of the base portion 63 a. On acircumferential edge portion of the seat surface, the base portion 63 ahas a ring-shaped surface that supports the spring 46. The height of theseat surface is adjusted to allow spring spacing for realizing arequired biasing force. The projection portion 63 b is formed so as toproject inside the pump chamber 41, and the projecting height anddiameter are adjusted such that the volume inside the pump chamber 41becomes a volume for realizing a required discharge pressure. In otherwords, the valve body 62 adjusts the biasing force of the spring 46 andthe volume of the pump chamber 41 using the base portion 63 a and theprojection portion 63 b.

The hollow portion 62 a formed inside the valve body 62 runs through anaxial center inside the base portion 63 a from a back surface of thebase portion 63 a, and extends to the vicinity of a proximal end insidethe projection portion 63 b, with the ball 64, the spring 66, and theplug 68 incorporated in that order inside the hollow portion 62 a. Theintake check valve 60 can thus be made compact because the axial lengthof the valve body 62 need only correspond to a length required forincorporating the ball 64, the spring 66, and the plug 68.

When a differential pressure (P1-P2) between a pressure P1 on the intakeport 49 side and a pressure P2 on the pump chamber 41 side is equal toor greater than a predetermined pressure that overcomes the biasingforce of the spring 66, the spring 66 contracts and causes the ball 64to separate from the center hole 69 of the plug 68, thereby opening theintake check valve 60. When the differential pressure (P1-P2) describedabove is less than the predetermined pressure, the spring 66 elongatesand causes the ball 64 to press against the center hole 69 of the plug68, thereby blocking the center hole 69 and closing the intake checkvalve 60.

The discharge check valve 70 includes: a ball 74, a spring 76 thatapplies a biasing force to the ball 74; and a plug 78 as a ring-shapedmember that has a center hole 79 with an inner diameter smaller than theouter diameter of the ball 74. The spring 76, the ball 74, and the plug78 are incorporated in that order from an opening portion 52 b of thehollow portion 52 a of the piston 50, and fixed by a snap ring 79.

When a differential pressure (P2-P3) between the pressure P2 on the pumpchamber 41 side and a pressure P3 on the discharge port 43 side is equalto or greater than a predetermined pressure that overcomes the biasingforce of the spring 76, the spring 76 contracts and causes the ball 74to separate from the center hole 79 of the plug 78, thereby opening thedischarge check valve 70. When the differential pressure (P2-P3)described above is less than the predetermined pressure, the spring 76elongates and causes the ball 74 to press against the center hole 79 ofthe plug 78, thereby blocking the center hole 79 and closing thedischarge check valve 70.

In the cylinder 42, the pump chamber 41 is formed by a space that issurrounded by an inner wall 42 b on which the piston body 52 slides, asurface of the piston body 52 on the spring 46 side, and a surface ofthe valve body 62 of the intake check valve 60 on the spring 46 side. Inthe pump chamber 41, when the piston 50 moves by the biasing force ofthe spring 46, the volume inside the pump chamber 41 increases andcauses the intake check valve 60 to open and the discharge check valve70 to close, thereby suctioning the hydraulic oil through the intakeport 49. When the piston 50 moves by the electromagnetic force of thesolenoid portion 30, the volume inside the pump chamber 41 decreases andcauses the intake check valve 60 to close and the discharge check valve70 to open, thereby discharging the suctioned hydraulic oil through thedischarge port 43.

Also, the cylinder 42 is formed with the inner wall 42 b on which thepiston body 52 slides, and an inner wall 42 c on which the shaft portion54 slides. The inner wall 42 b and the inner wall 42 c are arranged in astepped configuration, and the discharge port 43 is formed at a steppedsection thereof. The stepped section forms a space that is surrounded bya ring-shaped surface of the stepped section between the piston body 52and the shaft portion 54, and an outer circumferential surface of theshaft portion 54. Because the space is formed on the opposite side ofthe piston body 52 from the pump chamber 41, the volume of the spacedecreases when the volume of the pump chamber 41 increases, and thevolume of the space increases when the volume of the pump chamber 41decreases. At such times, the change in the volume of the space issmaller than the change in the volume of the pump chamber 41, becausethe surface area (pressure-receiving surface area) of the piston body 52that receives pressure from the pump chamber 41 side is larger than thesurface area (pressure-receiving surface area) of the piston body 52that receives pressure from the discharge port 43 side. Therefore, thespace functions as a second pump chamber 56. In other words, when thepiston 50 moves by the electromagnetic force of the solenoid portion 30,an amount of hydraulic oil that corresponds to the difference in theamount that the volume of the pump chamber 41 decreases and the amountthat the volume of the second pump chamber 56 increases is deliveredfrom the pump chamber 41 to the second pump chamber 56 via the dischargecheck valve 70 and discharged through the discharge port 43. When thepiston 50 moves by the biasing force of the spring 46, an amount ofhydraulic oil that corresponds to the amount that the volume of the pumpchamber 41 increases is suctioned through the intake port 49 into thepump chamber 41 via the intake check valve 60, while an amount ofhydraulic oil that corresponds to the amount that the volume of thesecond pump chamber 56 decreases is discharged from the second pumpchamber 56 through the discharge port 43. Accordingly, one reciprocalmovement of the piston 50 discharges the hydraulic oil twice from thedischarge port 43, which can reduce discharge variation and improvedischarge performance.

According to the electromagnetic pump 20 of the embodiment describedabove, the valve body 62 of the intake check valve 60 is formed from astepped structure that includes the cylindrical base portion 63 a andthe truncated conical projection portion 63 b that projects from theseat surface of the base portion 63 a. In addition, the valve body 62 ofthe intake check valve 60 is also formed such that the base portion 63 ahas the ring-shaped surface that supports the spring 46 on thecircumferential edge portion of the seat surface, and the projectionportion 63 b projects inside the pump chamber 41. Therefore, the springspacing can be adjusted by adjusting the height of the seat surface ofthe base portion 63 a, and the volume inside the pump chamber 41 can beadjusted by adjusting the projecting height and diameter of theprojection portion 63 b. As a consequence, a simple structure canoptimize the biasing force of the spring 46 and the volume of the pumpchamber 41, and also further improve discharge performance.

Moreover, the hollow portion 62 a formed inside the valve body 62 runsthrough the axial center inside the base portion 63 a from the backsurface of the base portion 63 a, and extends to the vicinity of theproximal end inside the projection portion 63 b, with the ball 64, thespring 66, and the plug 68 incorporated inside the hollow portion 62 a.Therefore, the intake check valve 60 can be made more compact becausethe axial length of the valve body 62 need only correspond to the lengthrequired for incorporating the ball 64, the spring 66, and the plug 68.

In the electromagnetic pump 20 of the embodiment, the discharge checkvalve 70 is embedded in the piston 50. However, the discharge checkvalve 70 may not be embedded in the piston 50, and may be incorporatedinto a valve body outside the cylinder 42, for example.

In the electromagnetic pump 20 of the embodiment, the projection portion63 b of the valve body 62 has a truncated conical shape. However, thepresent invention is not limited to this example, and the projectionportion 63 b may have any shape, such as a cylindrical shape, providedthat the projection portion 63 b projects inside the pump chamber 41.

In the electromagnetic pump 20 of the embodiment, the hollow portion 62a of the valve body 62 runs through the inside of the base portion 63 afrom the back surface of the base portion 63 a, and extends to thevicinity of the proximal end inside the projection portion 63 b.However, the hollow portion 62 a may not extend to inside the projectionportion 63 b, In such case, the height of the base portion 63 a may beincreased to incorporate the ball 64, the spring 66, and the plug 68 inthe hollow portion.

The electromagnetic pump 20 of the embodiment is configured as a type ofelectromagnetic pump in which one reciprocal movement of the piston 50discharges the hydraulic oil twice from the discharge port 43. However,the present invention is not limited to this example. Theelectromagnetic pump 20 may be any type of electromagnetic pump providedthat the electromagnetic pump is capable of discharging the hydraulicoil in association with the reciprocal movement of the piston. Suchexamples include an electromagnetic pump that suctions the hydraulic oilthrough the intake port into the pump chamber when the piston isforwardly moved by the electromagnetic force from the solenoid portion,and discharges the hydraulic oil inside the pump chamber from thedischarge port when the piston is backwardly moved by the biasing forceof the spring, as well as an electromagnetic pump that suctions thehydraulic oil through the intake port into the pump chamber when thepiston is backwardly moved by the biasing force of the spring, anddischarges the hydraulic oil inside the pump chamber from the dischargeport when the piston is forwardly moved by the electromagnetic forcefrom the solenoid portion.

The electromagnetic pump 20 of the embodiment is used to supply ahydraulic pressure for turning on and off a clutch or a brake of anautomatic transmission mounted in an automobile. However, the presentinvention is not limited to this example, and the electromagnetic pump20 may be used in any system that transports fuel, transportslubricating fluid, or the like.

Here, the correspondence relation will be described between mainelements in the embodiment and main elements of the invention as listedin the Summary of the Invention. In the embodiment, the cylinder 42corresponds to a “cylinder”; the piston 50 to a “piston”; the solenoidportion 30 to an “electromagnetic portion”; the spring 46 to a “biasingmember”; the valve body 62 to a “support member”; the ball 64, thespring 66, and the plug 68 that constitute the intake check valve 60 toan “intake on-off valve”; the discharge check valve 70 to a “dischargeon-off valve”; the base portion 63 a of the valve body 62 to a “supportportion”; and the projection portion 63 b to a “projection portion”.Note that with regard to the correspondence relation between the mainelements of the embodiment and the main elements of the invention aslisted in the Summary of the Invention, the embodiment is only anexample for giving a specific description of a best mode for carryingout the invention explained in the Summary of the Invention. Thiscorrespondence relation does not limit the elements of the invention asdescribed in the Summary of the Invention. In other words, anyinterpretation of the invention described in the Summary of theInvention shall be based on the description therein; the embodiment ismerely one specific example of the invention described in the Summary ofthe Invention.

The above embodiment was used to describe a mode for carrying out thepresent invention. However, the present invention is not particularlylimited to such an example, and may obviously be carried out in variousembodiments without departing from the scope of the present invention.

The present invention may be used in the manufacturing industry of anelectromagnetic pump, and the like.

1. An electromagnetic pump comprising: a cylinder; a piston that canreciprocate inside the cylinder; an electromagnetic portion thatforwardly moves the piston; a biasing member that backwardly moves thepiston; a support member that supports the biasing member and, with thecylinder and the piston, defines a pump chamber; an intake on-off valvethat is incorporated into the support member, and allows a hydraulicfluid to move from an intake port to the pump chamber and prohibitsreverse movement of the hydraulic fluid; and a discharge on-off valvethat allows the hydraulic fluid to move from the pump chamber to adischarge port and prohibits reverse movement of the hydraulic fluid,wherein the support member includes therein a bottomed hollow portionaccommodating from the intake port side at least a portion of the intakeon-off valve, and a communication hole providing communication between abottom portion of the hollow portion on the pump chamber side and thepump chamber, and the support member is formed with a support portionthat supports the biasing member, and a projection portion that is incommunication with the communication hole and projects from the supportportion toward the piston side.
 2. The electromagnetic pump according toclaim 1, wherein a diameter of the projection portion on the piston sideis formed smaller than a diameter of the projection portion on thesupport portion side.
 3. The electromagnetic pump according to claim 2,wherein the projection portion is formed into a truncated conical shape.4. The electromagnetic pump according to claim 1, wherein the hydraulicfluid is discharged by the biasing member backwardly moving the piston.5. The electromagnetic pump according to claim 1, wherein the hollowportion of the support member is formed such that the bottom portion ismore toward the piston side than a support surface of the supportportion.